


Unexpected Developments

by ARHitms_12569



Category: Gravity Falls
Genre: Aged-Up Character(s), BAP AU, Explicit Sexual Content, Fluff and Smut, Horns, Human Form Bill Cipher, Human Form Tad Strange, Multi, Plot What Plot/Porn Without Plot, Shameless Smut, Tentacle Sex, Threesome - M/M/M
Language: English
Status: Completed
Published: 2016-01-23
Updated: 2016-01-23
Packaged: 2018-05-15 15:55:19
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,265
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5791606
Author URL: https://archiveofourown.org/users/ARHitms_12569/pseuds/ARHitms_12569
Summary: <blockquote class="userstuff">
              <p>Dipper’s professor lets class out early, so he takes the opportunity to surprise his boyfriends, Bill and Tad, at home. Little does he know, the two demons have a surprise in store for him instead.</p>
            </blockquote>





	Unexpected Developments

**Author's Note:**

> I'm so sorry Mom. DX

It was a rare and happy day when Dipper Pines could walk home from school with a grin on his chubby cheeks and a spring in his step. Normally, he walked with his head down, dragging the daily baggage behind him in both a literal and figurative sense. But not today. Today, his peers had granted him a brief mercy from their incessant teasing of his size and his studies, and his professor had been uncharastically generous in dismissing class early. He felt light, knowing that he’d be able to surprise his boyfriends, Bill and Tad, at home because of this.

 

Dipper put the key in the lock, turning it quickly and quietly before opening the door just enough to squeeze his pudgy belly past the threshold to avoid the frame squeaking and giving away his location. The door quietly shut behind him with a click and he deposited his backpack and coat in the foyer, right next to Bill’s leather jacket and Tad’s purple suitcoat. He ran his fingers over both of them, bunching the fabrics in his hands and bringing them to his face. He nuzzled the articles of clothing, the familiar scents washing over him like a warm and comforting shower.

 

He was about to call out to Bill and Tad when a sudden wanton moan sounded from their shared bedroom. The noise made Dipper’s face heat up, turning his cheeks bright red to match his flannel shirt. He’d recognize Bill’s pleasured noises anywhere. The demon was exceptionally vocal in bed.

 

Another loud groan echoed down the hallway and without a second thought, Dipper quickly started stripping down. He kicked off his tennis shoes as his fingers worked quickly at the buttons on his shirt. When he was done, he threw the article of clothing carelessly over the back of the couch and checked his reflection in the mirror. He quickly tousled his hair to give himself a disheveled appearance before quietly sprinting down the hallway towards the master bedroom.

 

The door was ajar and through the crack, Dipper could hear the faint sounds of the mattress creaking underneath the weight of his two partners. With a roll of his shoulders, he pushed the door open.

 

The sight that greeted him was not what he had been expecting, to say the least.

 

Tad was reclined against the headboard, his relaxed posture and smug expression screaming fierce regality. He could have passed for calm and collected were it not for his hand wrapped languidly around his swollen cock, standing proudly at attention between his thighs. Pearly white precum pooled at the tip before spilling onto his hand as he slowly worked it up and down his length. But what surprised Dipper was not the sight of one of his boyfriends masturbating. It was the several dark purple tentacles that were snaking their way from behind his back, pulsing and shiny from some sort of natural lubricant: some were thick, others small. 

 

Even more shocking was what, or rather, who, those tentacles were holding in the air several feet above the bed.

 

Bill, in Dipper’s current and humble opinion, had never looked more vulnerable in all the time he’d known him. So many of Tad’s tentacles were wrapped securely around him, holding him up high and displaying him in the most vulgar of ways. Two were coiled firmly around his legs, fixing his thighs to his calves and spreading them wide. Another two were wrapped firmly around two ebony horns that had sprouted from Bill’s forehead, tugging his head back harshly and at such an angel Dipper was afraid his neck would snap. He knew that wouldn’t be the case, however. Tad loved Bill too much to truly harm his human vessel. One tendril held his hands securely behind his head so that his back arched and his elbows pointed towards the vaulted popcorn ceiling. The remaining tentacles were either adding extra support by wrapping around his waist and neck or working their way in and out of Bill’s ass, long and slow thrusts synching up with the pace that Tad’s hand had set. Dipper couldn’t help but notice the substantial wet spot that had pooled on the sheets beneath the blond demon and the way his straining cock was still leaking fluids.

 

It almost made Dipper jealous, mesmerized by how Tad could reduce such a dominant personality like Bill’s to a moaning, trembling mess. His jeans grew tighter at the sight of the blond being abused, of his pronounced Adam's apple bobbing hypnotically as he tried to swallow down his moans.

 

“Oh, come on, my dear,” Tad suddenly said in a low, husky voice, his lips quirking up into a smirk, “I know you can spread your legs further than that.” The multiple tentacles in Bill’s ass gave a strong ripple while the ones around his horns tugged even harder, causing the demon’s neck to crack. The sharp sound grated and vibrated in Dipper’s eardrums and he felt his cock twitch in his pants. The pressure was almost painful and it made his head spin.

 

Bill whimpered in the back of his throat, a noise so submissive that Dipper, for a moment, could not believe had come from his dom. His hips shifted and rolled as he tried to open his legs further, but he was unable to do so with the tight grip Tad’s extra appendages had on him.

 

“You’re so beautiful, Bill,” Tad sighed, a purple appendage snaking its way to caress at Bill’s cheek before pushing against his lips, silently asking for permission to enter his warm and wet mouth. The blond parted his swollen lips with a gasp, drool sliding down out of the corners of his mouth as the appendage lightly shoved its way inside, slithering deep into his throat. “Such a good boy, showing yourself off to me so well. My dear Bill, once we’ve taken care of you, you can put that pretty mouth of yours to good use. Would you like that?”

 

Bill twitched and choked, nodding and moaning as his eyes fluttered shut, the sound muffled by the tentacle. Dipper gasped at the noise, shivers racking their way up and down his spine. He reached down and absentmindedly palmed his hard arousal through his jeans.

 

Suddenly, the near constant motion of the tentacles stilled and Dipper and Tad locked eyes. Bill whined at the lack of movement, still oblivious to the observer, and attempted to rock his hips back on Tad’s tendrils.

 

Fuck, Dipper thought, a lump forming in his throat that he tried and failed to swallow down.

 

“D-Dipper!” Tad stuttered, his tentacles quickly dissipating, roughly dropping Bill back down on the bed. The blond was about to protest the sudden withdrawal until he too noticed his brunette lover standing in the doorway, eyes wide as saucers and pupils dilated, black overtaking his brown eyes. Tad made a move to get up.

 

“N-no,” Dipper suddenly cried out, voice cracking in his panic. Tad and Bill stared at him, both wearing dual expressions of concern while simultaneously still bearing the slightest remains of lust. The brunette swallowed again and squeezed his eyes shut, trying to recall the sight he had observed only seconds before. “D-don’t stop. Dear God, please don’t stop.” He opened his eyes again, quickly walking forward and climbing onto the bed with his boyfriends. With no hesitation, he crashed his lips to Bill’s, wincing as their teeth clacked together harshly but ignoring the subsequent pain in his lustful haze.

 

Bill’s strong arms came up to wrap around Dipper’s broad shoulders, pulling him close and shoving him down onto the bed. He nestled his weight between the teen’s legs, feeling his erection press against his stomach through the fabric of his pants. The demon pulled away, kissing and biting down the brunette’s torso, leaving his already-swollen lips unattended and open for Tad to sweep in and claim them with a sigh from both men.

 

“Are you okay with this, darling?” Tad asked against Dipper’s panting mouth, nipping quickly at his bottom lip. The teen whined, nodding furiously and bringing his hand around to wrap around the nape of Tad’s neck, pulling the dark-haired man to his open mouth once more. The demon thrust his tongue past his lover’s lips, swallowing the boy’s moans. With slitted eyes, Tad looked to where Bill was settled between Dipper’s thighs, his fingers lazily tracing circles just above the waistline of the brunette’s jeans. Purple eyes met gold as Tad slowly nodded at Bill, silently commanding him to remove the teen’s pants. The blond groaned at the look in his dom’s eyes before taking the metal zipper between his teeth and tugging it down, eyes locked on Dipper’s face and the way his eyebrows knit together in pleasure. He breathed heavily through his nose, the musty scent of Dipper’s arousal flooding his senses and driving him up the wall as he yanked the teen’s jeans and boxers off his legs.

 

Dipper lifted his hips and helped kick off his pants, gasping as his erection sprung free from it’s confines, the cooler air of the bedroom licking at his heat. His head tilted back, leaning against the pillow and Tad took the opportunity to drag his tongue along the brunette’s exposed neck, causing him to shiver and tremble. The demon felt a rippling along his lumbar spine as his purple tendrils slowly unfolded themselves from his back.

 

Meanwhile, Bill’s hand found its way between the teen’s legs, rubbing his middle finger against his puckered entrance as he climbed back up his pale body. The brunette whined at the pressure, rocking his hips back against Bill’s hand. When one of Tad’s smaller tentacles joined in, circling along with Bill, Dipper nearly cried. He bit down on his knuckles, whimpering into the skin there.

 

“Get that hand out of your mouth,” Bill ordered with a smirk, leaning down and pecking his cheek, “And spread your legs a bit more, kid.” Dipper did so unabashedly, presenting himself for both demons with nothing covering him but the dark blush that crept from his cheeks to his heaving chest. His hand came down to tweak at one of his nipples.

 

“God,” Tad sighed, one of his tentacles snaking around to wrap lazily around the human’s cock, causing said human to moan in relief, “We are so lucky to have you, Dipper Pines.” Bill nodded in agreement before carefully pushing past the ring of muscle, working his middle finger inside his lover. Dipper sobbed, his hips shifting against the familiar feeling of being prepared by the blond. Before long, the tentacle that had been pressed against him slipped inside as well. The two intrusions scissored him open, loosening him up for the main event. Because of how often the three had sex, it didn’t take long before he was ready.

 

Bill went to flip Dipper over onto his stomach when Tad stopped him, getting up and wrapping his arms around the blond’s waist from behind.

 

“No,” He whispered into his lover’s ear, biting down on the lobe, “I want him to see your face tonight.” Dipper felt his cock twitch at the prospect and he moaned in the back of his throat. Tad smiled sweetly down at the brunette over Bill’s dark shoulder, winking at him. “You always make the prettiest faces, my dear Bill.” At this, seemingly to prove his point, Tad slowly sheathed himself inside Bill.

 

The change was instantaneous. The cocky smirk that was as much a part of Bill as his own flesh and blood was quickly replaced with an open mouthed, furrowed eyebrow expression of pleasure. A faint blush colored his dark skin and his eyes squeezed shut. A long, loud keen was forced from his lips as Tad buried himself up to the hilt in his submissive lover.

 

As if Dipper’s blush wasn’t dark enough.

 

“This is a treat,” He admitted, reaching to grip Bill’s waist as the demon thrust into his human. The sensation of being filled felt good, amazing even, like it always did. Especially when the demon’s cock rocked firmly against his prostate, the pressure on the sensitive bundle of nerves casting thousands of stars across his vision. But Dipper Pines was finding a new pleasure in this position that he had rarely experienced before. He could feel the muscles flexing and tensing underneath Bill’s dark skin as he moved his hips, grinding fluidly into him. He moved his hands from the blond’s waist to his back, determined to indulge himself and feel every inch of his gorgeous lover while he still had the chance. 

 

Bill loved taking him from behind too much for this position to become commonplace.

 

“Scratch him, darling,” Tad commanded, tentacles crawling along both of the men beneath him. One pressed its way past the dark haired demon’s member, helping to penetrate Bill by pressing against his prostate whenever the dom’s cock was pulled back. Another went to coil tightly around Dipper’s leaking prick, stroking along with the rapid pace all three of them set. A choked moan left his mouth, the treatment to his neglected arousal causing him to dig his blunt nails harshly into Bill’s rippling back. The demon groaned, burying his face into the juncture between the teen’s neck and shoulder before biting down hard.

 

Dipper cried out, tilting his head to expose more of his neck for his lover to abuse. All he wanted was more, more, more. Every fiber of his being screamed for it along with his mouth in beautiful harmony. When he found the strength to open his eyes, not even realizing he had closed them, he was met with the two black horns protruding from Bill’s skull right next to his face. They were beautiful. Dark, coiled, curved and sharp. Elegant and dangerous.

 

Just like their owner, Dipper thought with a fond and adoring smile, kissing his dom’s cheek and tugging lightly at the demon’s hair.

 

Tad noticed where his human was looking and a devious smirk crossed his face. Reaching around Bill’s thrusting body, he entwined his fingers with those of the teen. He brought the hand to his face and pressed several tiny kisses to the unmarred flesh of his knuckles and one long, deep kiss to his palm before guiding it to wrap around one of Bill’s horns. Dipper gasped when he felt Bill’s cock twitch within him, and his thrusting picked up pace.

 

“You are ahhh~absolutely evil, St-Srange,” Bill moaned as his hips rocked faster and harder into the human writhing beneath him. Tad chuckled, licking a stripe from between the blond’s shoulder blades to the nape of his neck. He gripped Dipper’ hand tighter to the horn before stroking it up and down.

 

The teen marveled at the way the horn felt beneath his palm. Rough, but soft. And warm. So very, very warm. He could feel each individual ridge as his fingers tugged gently on it. So mesmerized he was that he almost didn’t notice how the already breakneck speed Bill was setting was rapidly increasing until the demon cried out right next to his ear.

 

“Aaah! P-Pine Tree, st-stop,” He moaned, his hips snapping between Dipper’s and Tad’s in a jerky, uneven rhythm, “I’m gonna-”

 

“Oh!” Dipper exclaimed, quickly letting go of the horn as realization dawned over him, “Sorry.” Bill shook his head with a small smirk playing on his lips. He opened his mouth to let his human know that it was alright, when suddenly two fingers crawled around the side of his face and inserted themselves into his mouth.

 

“Don’t apologize,” Tad smirked, eyes fluttering close as Bill’s too-long tongue eagerly wrapped around his fingers. Dipper felt the heat in his stomach coil at the sight and he reached between himself and the blond to help Tad’s tentacle jerk him off. “Keep going. The Pharaoh likes being touched like a common whore.” A loud keen vibrated in the back of Bill’s throat at the dirty talk as Dipper quickly gripped his horn once more, firmer and more confidently this time.

 

“Aah! Bill~” The brunette moaned, licking his lips as he felt the coil within him tighten rapidly. Suddenly, he snapped with a loud cry of his dom’s name falling off his lips, warm cum coating both of their stomachs. He gasped at the overstimulation as Bill continued thrusting into him, desperately chasing his own climax. A fox forever pursuing a too-quick and too-cunning rabbit.

 

Peeking out from behind his eyelashes, Dipper was able to judge from the way the demon had collapsed with his elbows on either side of his head that Bill was close, the gentle caress of his horn quickly pushing him over the edge.

 

“Fuuuck~” Bill groaned low in his throat, fully sheathing himself inside Dipper as he came. The teen threw his arms around the blond’s shoulders as his hips weakly jerked into him, pressing soothing kisses to his lower jaw as the two of them came down from their highs.

 

Tad pecked behind Bill’s ear as he continued on his own pursuit of pleasure, occasionally murmuring quiet apologies into the back of the blond’s head as small whines spawned from his sensitivity were coaxed out with every thrust. Dipper didn’t miss the smile that crossed Tad’s face and the way his eyebrows furrowed in adoration at the two men beneath him when he finally and silently came, hips pressed flush to Bill’s backside.

 

The three laid there for several minutes, catching their breath and whispering comforting sweet nothings to each other.

 

“You both did so good,” Tad praised, his tentacles vanishing in a whisp of purple smoke and slowly pulling out of Bill. “I’m so proud of my boys.” 

 

Bill shivered as Tad’s cum flowed freely out of his asshole, dripping onto the bedsheets. The same process was repeated when Bill withdrew from Dipper. With slow, lazy movements, Bill turned and pressed a kiss to Tad’s swollen lips, panting against his mouth. His horns slowly crawled back into his skull as his dick softened. The dark haired man smiled against the other’s lips, bringing one hand up to thread carefully into the long blond locks he loved so much and the other snapping briskly, cleaning up both themselves and their sheets.

 

A disgruntled grunt distracted their attention from each other and turned it to the exhausted human lying back against the pillows, his arms outstretched and waiting for two demons to occupy them.

 

“What am I?” Dipper laughed tiredly, wiggling his fingers at his demons, “Chopped liver?”

 

“Hush, Sapling,” Bill chuckled, lying down and wrapping his arms protectively around his lover with Tad following suit and mirroring him on Dipper’s other side. The brunette’s hands found their way to cup both of his boyfriend’s cheeks, lightly and affectionately scratching the smooth flesh found there, as he gazed at this with half-lidded, love filled eyes.

 

Tad pressed a kiss against his human’s temple while his fingers carded through Bill’s blond hair, now void of his dark horns.

 

“Care to see us off, my dear?” Tad asked softly, sensing Dipper’s eyes about to flutter shut in exhaustion. Bill nodded, grinning at the sight of his two lovers so worn out, before brushing his palm over Dipper’s birthmark and then his thumb over Tad’s cheekbone. He watched with amusement in his eyes and love in his heart as his two favorite people drifted off to a peaceful sleep. He pressed his lips to Dipper’s messy hair before closing his eyes and falling asleep with a content smile crossing his face.


End file.
